1. Field of the Invention
The present invention relates to a method and program for designing a semiconductor device and, more particularly to, a method and program that can reduce power supply noise of a semiconductor device.
2. Description of Related Art
For stable operations of a semiconductor, it is indispensable to design it so that power supply noise may be grasped early and reduced, which is critical especially for a high-speed, large-scale semiconductor in recent years. Work for reduction of a power supply noise value involves feedback to design parameters for the grasping of the noise value and the reduction of the noise. A method for grasping the power supply noise value in a conventional semiconductor integrated circuit design method is shown in FIG. 12. First, a circuit is produced by performing logic synthesis (S101). This produced circuit is laid out (S102). Then, noise is verified (S103).
A method for verifying the noise at S103 is shown in FIG. 13. The process divides the laid-out integrated circuit into blocks (S111) and simulates each of the circuit blocks (S112), to obtain a current waveform of each circuit block (S113). The process configures a model that can express the current waveform (S113) of each circuit block by using an inverter and a load capacitor. The process gathers such models to create a noise simulation circuit (S114) and performs analog simulation on this noise simulation circuit (S115). The process obtains a voltage or current waveform on the noise simulation circuit (S116). The process performs FFT analysis on the obtained voltage or current waveform (S117) and, after a noise distribution is grasped (S118), goes to S104.
The process decides noise (S104) and, if a noise value is not tolerated, returns to S101 or S102 to perform the flow again. If the noise value is tolerated, the process ends design (S105). It is to be noted that as arts related to the above, Japanese unexamined patent publication No. H11(1999)-120214 and Japanese unexamined patent publication No. 2001-175702 are disclosed.